Osamu Ohkubo

Crack Morphology and Corrosion after Bulge-press Forming of TiN and Ti Films Deposited on Stainless Steel Sheets Using Hollow Cathode Discharge Ion Plating Method

The crack morphology and corrosion for TiN and Ti films deposited on stainless steel sheets has been studied. After the bulge-press forming and the corrosion test, scanning electron microscope (SEM) observation were done on the surface and cross-section of films of the central parts of press formed area.The TiN films showed the comparatively sharp straight cracks characteristic of ceramics, whereas the Ti films cracked in the slightly elongated manner characteristic of metal, with scribing on the surface due to the soft Ti films.After the corrosion test, the TiN films were corroded remarkably, whereas the Ti films were masked with thin oxides. In particular, the oxides on TiN were different from those on Ti.It should be noticed that the TiN films were more susceptible to corrosion than the Ti films, presumably because the cavities and oxides created by internal peeling in TiN films exposed a greater area of steel and tended to trap corrosive substances.